The present invention relates to the cutting, milling and similar kinds of shaping of curved surfaces, particularly plate to be used in molds for casting, under utilization of certain predetermined control parts for the cutting tool, using e.g. curved tracking on the basis of suitable templates.
Devices and methods of the kind to which the invention pertains are fairly well known. Exemplary here are for example German printed patent applications Nos. 28 00 525 and 25 44 604. The devices disclosed therein are fairly sophisticated, particularly as far as multiple curved surfaces of large extension are concerned. This is needed e.g. for molds for continuous casting, particularly the broad plates of molds for the casting of slab ingots. This type of molds are constructed generally from individual plates made of copper and one distinguishes longitudinal or wide plates from short or transverse plates, four in total and being arranged in a boxlike configuration, the "box" being open in the top and the bottom. The molten metal is poured into the mold from above and since the mold is strongly cooled to solidified shell or skin forms in the mold and emerges as a casting ingot from the bottom. The interior of the casting is still liquidous at this point but that liquidous core will solidify at some point downstream from the mold.
Molds for slab ingots are usually constructed to have a certain curvature at a relatively large radius (6 to 15 m) casting is basically and usually carried out vertically owing to the utilization of the force of gravity but the continuousness requires that the casting is veered into the horizontal. The curvature of the mold does match the curvature of that veering path. The mold wall plates have to be shaped i.e. curved accordingly.
The operator in a general sense usually requires casting to be very accurate simply because the customer in turn requires certain qualities in the product. This means that the continuous casting mode and the machiens generally have to meet certain standards and requirements which include particularly an accurate construction of the mold plate. Such requirement is of course imposed upon the maker of the mold. In particular it is necessary to make the mold through cutting operation and milling or the like such that the plates are accurate in terms of predetermined dimensions with emphasis on reproducibility of results. This way it will be possible to satisfy strict requirements of accuracy in the continuous casting process.
The known structures were indeed able to fulfill many requirements. However difficulties arise when the mold is, in addition, having a certain funnel configuration i.e. if it is supposed to narrow or taper down, in the direction of casting. This tapering is shown e.g. in European Pat. No. 149734. A funnel shaped entrance is provided through appropriate configuration of the mold plates. Narrow sides of the mold taper and owing to the funnel shape the additional requirement exists that the content of the mold is moved and flushed through, particularly the molten material is to be uniformly distributed. On the other hand the further requirement exists that as far as mold construction and operation is concerned, the formation of longitudinal fractures and other perforation must be avoided; rupture of the skin might have catastrophic results. Thus, the funnel shaped enlargement of the upper mold part must not pose problems in this regard.
The cutting of the mold plates generally and the cutting process as far as adaptation to the funnel shaped requirement is concerned poses certain problems. These problems are compounded if the mold is to be curved, i.e. a curvature is to be superimposed upon the taper. Moreover, the curvature is conceivably not in one but two dimensions. Additionally geometric matching is required throughout. This matching includes the funnel shape requirement, which as already stated compounds the complexity of the mold surface to be made. Hence not just the mold but also the upper portion into which the molten metal is poured, should have a funnel shape with matched curvature.
In the past these specific details and requirements turned into a requirement of manual labor. A mold and mold plates which exhibit the desired funnel shaped entrance under observance of the curvature at the desired accuracy required very much the accuracy of a skilled artisan.